The UK’s largest NHS-approved online pharmacy has been instructed to "raise their game" after warning patients prescriptions will be hit by severe delays over Christmas.

Pharmacy2U have cited the transfer a new automated facility as the reason for the disruption that could leave patients without medication over the festive break.

The online outfit, that previously hit the headlines for unlawfully selling patient data, are now facing a joint inspection from NHS England and the General Pharmaceutical Council (GPhC).

An NHS England spokesperson said: “Frankly this performance isn’t good enough and Pharmacy2U are going to need to raise their game.”

Their comments came after the company announced they would not be able to deliver prescriptions until the week commencing 11 January 2016.

They added: “Any prescriptions they can’t service can be dispensed by another pharmacist, therefore patients whose prescription are likely to be affected should contact a local pharmacy or if necessary, their GP, as soon as possible to ensure that they have a supply of their medicines to cover the festive period.”

Meanwhile the GPhC has voiced support for NHS England’s stance.

Their spokesperson said: “We are aware of concerns relating to Pharmacy2U’s prescription medication delivery and we are carrying out a special inspection visit alongside NHS England.

“We would advise any patients concerned about their medicines delivery to follow NHS England’s advice.”

Daniel Lee, managing director and superintendent pharmacist of Pharmacy2U, has issued an apology for the “unforeseen difficulties” and said the dispensary team are working 24 hours a day to continue dispatching medication.

The troubled pharmacy was previously fined £130,000 for unlawfully selling the personal details of 21,500 patients and customers to third party companies, including one that was under investigation for fraud.

The fine followed an investigation by the Information Commissioner’s Office.